Physiology Flashcards by Emily Christie

What is an intrinsic control system?

System to maintain homeostasis within an organ

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What is an extrinsic control system?

A system to control homeostasis initiated outside an organ

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What is a feedforeward system?

A response in anticipation to a change

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What does positive feedback do?

A response after a change that amplifies that change (ie contractions in labour)

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What does negative feedback do?

A response that occurs after a change that opposes the initial change

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What is blood pressure?

The outwards pressure by the blood on the vessel walls

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What is systolic BP a measure of?

Pressure excerted during heart contraction

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What is diastolic BP a measure of?

Pressure excerted when the heart relaxes (dia-dies)

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What is pulse pressure?

Systolic - diastolic

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What is a normal systolic and diastolic?

Systolic <140mmHg at rest

Diastolic <90mmHg at rest

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What is a normal pulse pressure?

30-50mmHg

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What is the mean arterial BP?

The average pressure over 1 cardiac cycle

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How do you calculate the MAP?

[(2×diastolic) + systole] ÷ 3

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What is the normal range for MAP?

70-105mmHg

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What is the minimum MAP needed to peruse vital organs?

60mmHg

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How else can you calculate the MAP (apart from using systole and diastole)?

MAP = CO × SVR

MAP = SV × HR × SVR

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How do you calculate the cardiac output?

CO = SV × HR

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What is the cardiac output?

The volume of blood pumped per ventricle per minute

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What is the stroke volume?

Volume of blood pumped by each ventricle per heart beat

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What can you alter to control blood pressure?

Stroke volume
The heart rate
The systemic resistance

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Which part of the nervous system controls the heart rate?

The autonomic nervous system

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What part of the ANS increases the heart rate?

Sympathetic

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What effect does the parasympathetic division of the ANS have on heart rate?

The division of the vagus nerve decreases heart rate

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Does vasoconstriction increase or decrease SVR and MAP?

Increase

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How can heat be exchanged to the external environment?

Radiation Evaporation Conduction Convection - forced air movement

What do tight junctions do?

Join the lateral edges of epithelial cells near their apical membranes

What do desmosomes (anchoring junctions) do?

Link adjacent cells tightly to provide mechanical strength

What do gap (communicating) junctions do?

Allow the movement of ions and molecules between adjacent cells

What 5 factors influence diffusion across the membrane?

The magnitude of the concentration gradient The surface area of the membrane The lipid solubility of the substance The molecular weight of the substance The distance through which diffusion is taking place

What is tonicity?

The effect a solution has on cell volume | Can be iso- hypo- or hyper-

What does isotonic mean?

There is no movement of water, therefore no change in cell volume

What does hypotonic mean?

Water moves into the cells causing them to swell.

What does hypertonic mean?

Water moves out of the cell, causing the cell to shrink

What does the sodium, potassium ion pump do?

Helps to establish sodium and potassium in concentration gradients For every 3 Na+ out 2K+ go in

What are the two types of vesticular transport and do they require energy?

Exocytosis Endocytosis Yes - active process

What is the membrane potential?

The separation of opposite charges across the membrane due to differences in the concentrations and permeability of ions

Which cells produce action potentials when they are excited?

Nerve and muscle cells

Is the concentration for K+ ions outwards or inwards?

Outwards

If the permeability of Na+ ions is increased across a cell membrane what happens to the membrane potential?

It is driven closer towards the Na+ ions equilibrium potential. So the membrane potential is increased

What is the resting membrane potential?

-70mV

What is the equilibrium potential for K+ ions?

-90mv

What is the Nernst equation and what is it used for?

Eion = 61log10 [ion]outside/[ion] inside Used to calculate the equilibrium potential for any given ion

what is the equilibrium potential for sodium ions?

+61mV

What formula is used to calculate the resting membrane potential?

the goldman-hodgkin-katz equation

what happens during depolarization?

the membrane potential becomes less negative

what happens during hyperpolarization?

when the membrane potential becomes more negative

what happens during repolarisation?

the depolarised state returns back to the normal resting value

Passive movement of an ion through an ion channel is driven by...

the electrochemical gradient for that ion

Why do sodium ions flow inwardly?

the concentration gradient is inward | the electrical gradient is inwards

why do potassium ions flow outwardly?

because the concentration gradient is outwards and the energy of that exceeds that of the electrical gradient which is inwards

if lots of sodium ion channels are open, what effect does this have in the membrane potential?

it increases towards the equilibrium potential for the sodium ions

what can ion channels be gated by?

LGICs VGICs Physical stimuli - for example mechanical stretch

which type of ion gated channel is responsible for the action potential in neurons?

VGICs

what is an action potential?

An all or nothing, brief electrical signal in which the polarity of the membrane is momentarily reversed

when are action potentials generated?

when the threshold is reached

what is the upstroke in an action potential caused by?

the opening of sodium ion channels - causing depolarization

what is the downstroke caused by?

the opening of potassium ion channels and the inactivation of sodium ion channels

what is the undershoot caused by?

the delayed closure of the voltage activated potassium ion channels

what 3 states do voltage gated sodium ion channels exist in?

closed open inactivated

what is needed for the sodium ion channels to return to its closed state?

repolarisation

how can you increase passive current speed in a nerve fibre?

increasing the diameter of the axon or add an insulating material (myelin) to decrease the leak of current across the axon

How are impulses sent in myelinated axons?

by saltatory conduction - the signal jumps from one node of Ranvier to the next

what happens to the action potential in un-myelinated axons?

there is a passive (leaky) spread of current

what are the pre and postganglionic neurotransmitters in the parasympathetic division?

Acetyl choline for both

what are the pre and postganglionic neurotransmitters for the sympathetic division?

pre = acetyl choline post = noradrenaline

how is a neurotransmitter's release via exocytosis induced?

by calcium ion influx through voltage activated calcium channels